1. Field of the Invention
This invention relates to a novel process for preparing partially crystalline polyacetylene in the cis or trans configurations by polymerizing acetylene in the presence of a .mu.-(.eta..sup.1 :.eta..sup.5 -cyclopentadienyl)-tris(.eta.-cyclopentadienyl)dititanium (Ti-Ti) catalyst and also to stable polyacetylene "gel" compositions produced from the process comprised of a polyacetylene, and gel-forming liquid therefor.
2. Brief Description of the Prior Art
Partially crystalline forms of polyacetylene, in the cis or trans configurations, when "doped" with a controlled amount of an electron-attracting species such as a halogen-containing compound, like iodine or arsenic pentafluoride, are known to exhibit increases in conductivity over a remarkably wide range of up to about 11 magnitudes. See J. Am. Chem. Soc. Vol. 100, 1013-1015 (1978), Chemical and Engineering News, pp. 19-20 (April 14, 1978), J. Chem. Phys. 68, pp. 5405-5409 (1978) and J. Chem. Phys. 69, pp. 106-111 (1978). The "doped" polymers are capable of functioning as electrical conductors or semiconductors.
Catalytic methods for synthesizing polyacetylene in its respective cis and trans configurations are well known in the art and include the use of Ziegler-type catalysts, described for example in J. Poly. Sci. Polymer Chem. Ed. 2, Vol. 12, pp. 11-20 (1974); the use of copper-aluminum spinel solids, as described in Kinet. Katal. 12 (4), 974 (1971), Chem. Abstr. 76, 15005Y (1972); and the use of dicyclopentadienyl vanadium as described in Japanese Pat. No. 70 08,980 (1970), Chem. Abstr. 73, 67036s (1970).
The reference Bull. Chem. Soc. Japan, 38, 859-860 (1965) describes a method for polymerizing acetylene which involves a "titanocene"-type catalyst. However, subsequent work by others in J. Am. Chem. Soc., Vol. 92, pp. 6182-6185 (1970), disclosed that the above "titanocene" material, as prepared by reduction of bis dicyclopentadienyl titanium dichloride with sodium amalgam, actually used as a catalyst, was in fact a dimer of cyclopentadienyl fulvalene titanium hydride.
The references of Guido Pez in J. Am. Chem. Soc. 98, 8072 (1976), U.S. Pat. No. 3,776,932 (1973), Re 29,368 (1977) and U.S. Pat. No. 4,024,169 (1977), Allied Chemical being the assignee, disclose a novel cyclopentadienyl titanium compound, being .mu.-(.eta..sup.1 :.eta..sup.5 -cyclopentadienyl)-tris(.eta.-cyclopentadienyl)dititanium(Ti-Ti), for removing nitrogen gas from a mixture of nitrogen and argon. However no specific mention is made of the possibility of using the compounds as catalysts in the polymerization of acetylene.
There is a continuing need for new, inexpensive and conveniently prepared catalysts which will reproducibly polymerize acetylene into its respective cis and trans partially crystalline forms, useful as starting materials for preparing electrical conductors.
The reference, J. Poly. Sci., Part A-1, Vol. 7(12), pp. 3419-3425 (1969) describes a gel produced during the polymerization of acetylene using an iron dimethylglyoximate-2-pyridine/triethyl aluminum catalyst in which the weight of combined catalyst present is greater than the weight of polyacetylene produced, on a dry basis. No specific working properties of the gel is described and a solid polymer is recovered therefrom.
There is a continuing need in the art for formulations of polyacetylene which can be easily and conveniently fabricated into articles in which the polyacetylene is partially chain-aligned. Solid polyacetylene produced by conventional methods is generally intractable and insoluble in known solvents which renders the fabrication into isotropic, or anisotropic, i.e., partially chain-aligned, articles difficult.